1. Field of the Invention
The present invention relates to a robot and a manipulator that transmits mechanical power via a flexible power transmission member.
2. Related Art
There has been proposed a medical manipulator, such as robotic forceps for remotely operating surgical forceps (see Japanese Patent Laid-Open Pub. No. 2000-350735). Besides, there has been proposed a medical manipulator suitable for suture ligature (see Japanese Patent Laid-Open Pub. No. 2001-102248).
These conventional medical manipulators can be quickly manually operated by experts, and the experts can perform microscopic work by using them and can operate them from difficult angles. In particular, the manipulator has a bending or rotating joint at the tip thereof, so that the tip can be arbitrarily moved. Therefore, it is possible to easily perform suture and ligature from various directions, which are difficult for conventional forceps.
In addition, the robotic forceps can be used in combination with conventional surgical equipment. For example, an operator can use the robotic forceps with the right hand and a conventional forceps with the left hand. In addition, the robotic forceps themselves have a less complicated structure and require no expensive components, so that the robotic forceps has an advantage capable of fabricating it at low cost.
This kind of medical manipulator can be used for applications other than the medical application. For example, the manipulator is suitable for maintenance and repair at places where the operator cannot easily access, such as a narrow part of an energy device.
However, in the manipulators described in the above prior art documents, the manipulation section and the tip portion of the forceps are integrated with each other, and there are limitations on shape, dimensions and position of the power transmission mechanism between the manipulation section and the tip portion of the forceps.
Typically, a wire, a pulley or a link is used as the power transmission mechanism. For example, in a conventional power transmission mechanism using the wire and the pulley, if the diameter of the wire is small, or the distance between a driving pulley and a driven pulley is large, there arises a problem that elastic deformation (expansion) of the wire increases, and sufficient power transmission cannot be achieved. In addition, there is a problem that an adequate rotational rigidity cannot be achieved on the side of the driven shaft (output shaft) at a held state in which the driving pulley is fixed or at a servo lock state. If a desired rotational rigidity cannot be achieved, the intended operation cannot be carried out, and the operability and workability are reduced.
In addition, if an excessive load torque is imposed, the wire or a fastening part can be fractured. Furthermore, if the diameter of the pulley is not sufficiently larger than the diameter of the wire, a sufficient life cannot be obtained, and a fatigue fracture can occur. Furthermore, if the diameter of the pulley is sufficiently larger than the diameter of the wire, the power transmission mechanism becomes larger, and the rigidity thereof decreases.
On the other hand, in a conventional power transmission mechanism using a wire and a link, buckling of the link has to be taken into consideration. Thus, the link has to be sufficiently thick, or two links have to be disposed in parallel with each other. Accordingly, there are problems that the weight increases, and that a high component precision and a high assembly precision are required to dispose the links in parallel with each other. In addition, in the conventional power transmission mechanism using a link, the link cannot rotate to ±90 degrees, and thus, there is a problem that a sufficient range of movement cannot be ensured.